The case for local police having access to the FOID card database appears weak. Over and over, news reports of domestic disturbances in which firearms are involved indicate that the individual creating the problem did not have a FOID card. In view of that, it would seem foolish for police on the scene to assume there are no firearms present just because there is no record of a FOID card holder at the address. If they have to use the same degree of caution whether there is a FOID card holder or not, what is the value of their having access to the database?
On the downside, giving local police such access would greatly increase the number of people able to retrieve the data, and thus would also greatly increase the likelihood of some Edward Snowden-type individual making the data public, regardless of supposed controls put in place.
The state of Illinois has already decided, by way of a law recently passed, that making FOID card data public is not advisable. The risks outweigh the supposed benefits, in my opinion.